This one is way better [Youtube:MFCX28PxlNc]EDIT: damn how do I insert a youtube video again? ^^

You're close, but you do not need to capitlize the Y in Youtube.

So it's

[youtube: MFCX28PxlNc] ?

EDIT: Now neither the video NOR the code is shown actually between the "So it's" and the question mark there's the code but it doesn't show anything

Well then I'm just gonna post the link. Why doesn't NL just have a menu in the Post writing mode where you can just click on Embedd Youtube Video, Embed Picture etc. so I don't have to figure anything out myself